Images in Photoshop CS3

Transcription

1 Techniques for Optimizing Near UV Images in Photoshop CS3 Kevin Osborn October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 1

2 Background All images created using Fuju S3 Pro UVIR camera Nikon 50mm f/1.4 lens Full sun conditions Images captured in RAW and processed in Adobe Camera Raw and Photoshop CS3 Used Santa Barbara Mission for subject Masonry repair demonstrates UV capabilities October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 2

3 Compare to TMax 400film Digital October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 3

4 Introduction: The Problem Biggest problem is getting a pure near UV image. Easy to get near IR signal pollution. What can we do about it? UV signal gets spread amongst the RGB channels due to the Bayer filter array. How to make the best monochromatic UV image from this data. October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 4

5 Outline Perfecting the capture Three ways to create B&W image 1. Optimize blue channel 2. Using B&W adjustment layer 3. Blend channels Review results Demo techniques in Photoshop h Questions October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 5

6 Perfecting the Capture Focus Live Preview Flare Lens hood, cover eyepiece Effect of Exposure on UV signal Effect of ISO on digital it noise Effect of White Balance on image quality October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 6

7 Perfecting the Capture: Exposure Assumption: Blue channel is where most of the UV signal ends up What exposure is best for the blue signal? Test: Do a series of exposures and watch the channel histograms Use Photoshop to look at histograms All exposures made at f/11 at ISO images made at half stop increments October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 7

8 Exposures and Histograms 1 second 1.5 seconds 2 seconds 3 seconds 4 seconds October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 8

9 Exposures and Histograms 1 second 1.5 seconds 2 seconds 3 seconds 4 seconds October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 9

10 1.5 second exposure Camera vs. Photoshop Histograms 4 second exposure October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 10

11 Exposure Conclusions Color specific histograms on the Fuji are consistent with Photoshop s display Composite Master histogram on camera is vastly different from Photoshop s and doesn t indicate overexposure of the blue channel Blue channel clips first, avoid this October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 11

12 Perfecting the Capture: Effect of ISO Assumption: Noise is the worst in the blue channel Test: Compare noise in color channels for ISO values of: 100, 200, 400, 800 and 1600 Full sun, Daylight WB, Baader Venus filter Exposure info: f/11 ISO 100 f/11 ISO 200 f/11 ISO f/11 ISO f/11 ISO 1600 First, look at the extremes October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 12

13 ISO- Red Channel Exposure info: Full sun f/11 ISO f/11 ISO 1600 Daylight WB October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 13

14 Exposure info: Full sun ISO- Green Channel f/11 ISO f/11 ISO 1600 Daylight WB October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 14

15 Exposure info: Full sun ISO- Blue Channel f/11 ISO f/11 ISO 1600 Daylight WB October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 15

16 Closer look at Red Channel October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 16

17 ISO Conclusions Red channel starts to show noise at ISO Most noise is in the green channel, even at ISO 100 Little to no noise in blue channel at ISO 1600 though there is some degradation in sharpness Should optimize image for first blue channel, and then the red channel October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 17

18 Perfecting the Capture: Effect of White Ballance Does the white balance setting help to get the best exposure? Facts: WB does not influence what is captured in RAW but only the way the image is processed after capture The WB selection seems to impact the channel specific histograms on the LCD and thus will influence the exposure you choose Theory: Tungsten WB would favor the blue signal in an effort to cool the color temperature Test: Compare captures using Tungsten WB and Daylight yg WB October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 18

19 White Balance Daylight Tungsten October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 19

20 WB- Red Channel Exposure info: Full sun D - f/11 ISO 100 T - f/11 ISO 100 Daylight Tungsten October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 20

21 WB- Green Channel Exposure info: Full sun D - f/11 ISO 100 T - f/11 ISO 100 Daylight Tungsten October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 21

22 WB- Blue Channel Exposure info: Full sun T - f/11 ISO 100 D - f/11 ISO 100 Daylight Tungsten October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 22

23 White Balance: Conclusions Tungsten WB Can help to optimize exposure for blue channel Not much different from changing g the white balance after exposure but saves post processing time (as we will see in the next section) October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 23

24 Converting to B&W 1. Optimizing the blue channel in Adobe Camera Raw 2. Using B&W adjustment layer 3. Blend channels October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 24

25 1- Adobe Camera Raw Use color temperature slider to optimize the blue channel Use only that channel to create B&W image October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 25

26 1 - Adobe Camera Raw Blue signal Note: had to reduce exposure to avoid clipping October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 26

27 Baader Venus 2 filter Original Red Ch Green Ch Blue Ch October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 27

28 Just Blue Channel October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 28

29 Compare to B&W Film Baader Venus, Blue Channel TMax 400 with Xnite 330 October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 29

30 What about leaky filters? Will using only the blue channel help isolate the near UV signal? October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 30

31 With IR Pollution Filter stack: XNite 330 only blue shows UV signal Original Red Ch Green Ch Blue Ch October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 31

32 With IR Pollution Filter stack: XNite and UG-1 only blue shows UV signal Original Red Ch Green Ch Blue Ch October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 32

33 With little to no IR Polution Baader Venus 2 filter Original Red Ch Green Ch Blue Ch October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 33

34 Blue Channel XNite XNite & UG1 Baader Venus October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 34

35 2- Convert to BW Use Photoshop CS3 Black & White adjustment layer Select filter High Contrast Blue Filter October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 35

36 Results: B&W Adjustment Layer October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 36

37 3-Channel Blending Using the Baader Venus filter results in significant UV signal in other channels Would like to reassemble signal Blend red and blue channels for final image Select blue channel in channels palette Apply image: choose the red channel Overlay blend mode seems to work best Can optionally blend in the green channel too October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 37

38 Apply red channel to blue Add in 50% green channel October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 38

39 Comparison BW conversion Color o temperature e adj Blending Channels October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 39

40 Compare to Film Channel blend Baader Venus TMax 400 with XNite 330 October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 40

41 Conclusions B&W Conversion Blue channel optimization is effective even when there is near IR pollution B&W adjustment layer is effective but low contrast There may be some signal loss when using the Baader Venus filter and only using the blue channel Best approach is the Apply image or channel blend method because it recaptures es the signal from the red and, potentially, the green channels Adds contrast and preserves detail in highlights October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 41

42 Final Retouching Curves to bring down sky Curves to add local contrast October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 42

43 Demo Apply Image How to blend channels in Photoshop October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 43

44 Questions? Outside-In Photography October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 44

45 Links Shane Elen s site: October 4, 2008 Ultraviolet Imaging Symposium Kevin Osborn 45